Vehicles are typically equipped with brake systems for slowing or stopping movement of the vehicle in a controlled and safe manner. Parking brake systems (also known as emergency brake systems) may also be included to ensure the vehicle does not roll after the vehicle's engine has been turned off and/or the vehicle has been left unattended. One type of parking brake is known as a drum-in-hat parking brake. The drum-in-hat parking brake includes a brake drum attached to a wheel assembly of the vehicle with a pair of opposite disposed brake shoes positioned within the brake drum. A disc may extend from the brake drum and be part of a disc-brake system for the vehicle. When the parking brake is actuated (sometimes referred to as being “set”), an actuator forces the pair of brake shoes apart from each other and into contact with an inner surface of the brake drum such that a desired braking pressure is applied thereto. The desired braking pressure prevents movement of the brake drum, wheel assembly and vehicle. However, when a vehicle with a drum-in-hat parking brake is parked on an incline, a small amount of movement of the vehicle may occur after the transmission of the vehicle has been placed in Park, the drum-in-hat parking brake has been set and the driver has removed his/her foot from the vehicle brake pedal. The small amount of movement by the vehicle may result in rotation of the brake drum, additional spreading apart of the brake shoes within the brake drum and a decrease in parking brake pressure applied to the inner surface of brake drum by the brake shoes. Such a phenomenon, i.e., rotation of the brake drum after the drum-in-hat parking brake has been set and the corresponding spreading apart of the brake shoes is often referred to as “brake wrap” and must be accommodated for in order to ensure adequate braking force is applied to the wheel assembly while the vehicle is parked.
Recently, electrically actuated drum-in-hat parking brakes that employ electric actuators have been desired. However, current electric actuators have limited actuation movement to spread or move brake shoes within a brake drum apart from each other during brake wrap and the use of electrical drum-in-hat parking brakes that accommodate brake wrap has proven difficult.
Accordingly, an improved electrically actuated drum-in-hat parking brake would be desirable.